Fatty acid decarboxylases for sustainable linear α-olefin production: mechanisms, engineering strategies, and applications.

Linear α-olefins (LAOs) are important feedstocks for polymers, lubricants, and specialty chemicals, but their conventional manufacture remains dominated by petrochemical processes. Fatty acid decarboxylases offer a direct route from renewable fatty acids to one-carbon-shortened terminal alkenes under mild conditions. This review critically evaluates the heme-dependent enzyme OleT and the non-heme diiron enzymes UndA and UndB by linking mechanistic evidence to engineering and process decisions. The available data reveal an asymmetric knowledge base. OleT is the best-resolved platform and can operate with hydrogen peroxide or with oxygen coupled to either redox proteins and NAD(P)H or small-molecule reductants, but competing decarboxylation, hydroxylation, and oxidative inactivation constrain yield. UndB provides high decarboxylation selectivity and is attractive for whole-cell synthesis, whereas its membrane association, dependence on electron-transfer components, and lack of a high-resolution structure impede in vitro use and rational engineering. UndA requires fewer auxiliary redox components, but its low activity and unresolved order of Cβ-H and C-Cα bond cleavage limit predictive design. Across enzyme-engineering studies, improvements in conversion, selectivity, stability, and expression are not necessarily aligned, and comparisons are often confounded by non-standardized reaction conditions. We therefore assess driving systems, cell factories, cascades, and scale-up using common criteria that include olefin yield, total turnover, substrate loading, volumetric productivity, catalyst lifetime, and downstream compatibility. Priority research needs are evidence-resolved mechanisms, product-based multiobjective screening, standardized benchmarking, and integrated enzyme-process development. No single decarboxylase is universally superior. Platform selection should be determined by substrate class, required selectivity, reaction environment, and process configuration.